Field of the Disclosure
The field of the disclosure relates to methods or devices used to dissect tissue during surgery or other medical procedures.
Technical Background
Surgeons sever or separate patients' tissues as a major component of most surgical procedures. Called “dissection,” this is how surgeons tunnel from an accessible region of a patient to reach a target within. The two dominant dissection techniques are: (1) “sharp dissection,” where surgeons sever tissues with either scissors, scalpels, electrosurgical devices, and other cutting instruments; and (2) “blunt dissection,” consisting of separating tissues by controlled tearing of one tissue from another.
The advantage of sharp dissection is that the cutting instrument easily cuts through any tissue. The cut itself is indiscriminate, slicing through all tissues to which the instrument is applied. This is also the disadvantage of sharp dissection, especially when trying to isolate a first tissue without damaging it, when the first tissue is embedded in, and is obscured by, a second tissue, or more commonly, is enveloped in many tissues. Accidental cutting of a blood vessel, a nerve, or bowel, for example, is a constant threat for even the most experienced surgeons and can rapidly lead to serious, even life-threatening, intra-operative complications, with prolonged consequences for the patient. When employing minimally invasive procedures, for example laparoscopy or the use of a surgical robot, the chances of surgical error increase.
Isolation of a first tissue embedded in other tissues is therefore frequently performed by blunt dissection. In blunt dissection, a blunt instrument is used to force through a tissue, to force apart two tissues, or to otherwise separate tissues by tearing rather than cutting. Almost all surgeries require blunt dissection of tissues to expose target structures, such as blood vessels to be ligated, or nerve bundles to be avoided. Examples in thoracic surgery include isolation of blood vessels during hilar dissection for lobectomy and exposure of lymph nodes. In plastic surgery, blunt dissection comprises the lion's share of many procedures, consisting of undermining very large areas of the patient's skin, where poor blunt dissection can result in hematomas, dermal punctures, and necrosis of the skin.
Blunt dissection includes a range of maneuvers, including various ways to tease apart or tear soft tissues, such as the insertion of blunt probes or instruments, inverted action (i.e., spreading) of forceps, and pulling of tissues with forceps or by rubbing with a “swab dissector” (e.g., surgical gauze held in a forceps, or a purpose-built, disposable swab stick such as a Kitner). When needed, sharp dissection is used judiciously to cut tissues that resist tearing during blunt dissection.
The general goal of blunt dissection is to tear or otherwise disrupt occluding tissue, such as membranes and mesenteries, away from the target structure without tearing or disrupting either the target structure or critical structures such as nearby vessels or nerves. The surgeon capitalizes on the different mechanical behaviors of tissues, such as the different stiffness of adjacent tissues, or the existence of planes of softer tissue between firmer tissues. Frequently, the surgeon's goal is to isolate a target tissue that is mechanically firm, being composed of more tightly packed fibrous components, and is embedded in a tissue that is mechanically soft, being composed of more loosely packed fibrous components (for example, loose networks of collagen, reticulin, or elastin). More tightly packed fibrous tissues include tissues composed of tightly packed collagen and other fibrous connective tissues, usually having highly organized anisotropic distributions of fibrous components, often with hierarchical composition. Examples include blood vessels, nerve sheaths, muscles, fascia, bladders, and tendons. More loosely packed fibrous tissues have a much lower number of fibers per unit volume or are composed of less well organized materials such as fat and mesenteries. Fibrous components include fibers, fibrils, filaments, and other filamentous components. When a tissue is referred to as “fibrous”, the reference is typically to extracellular filamentous components, such as collagen and elastin—proteins that polymerize into linear structures of varying and diverse complexity to form the extracellular matrix. As mentioned in the previous paragraph, the density, orientation, and organization of fibrous components greatly determine the tissue's mechanical behavior. Sometimes, tissues are referred to as “tough, fibrous tissues” indicating that the fibrous or filamentous components are densely packed, organized, and comprise a significant fraction of the bulk of the tissue. However, all tissues are fibrous, to one extent or another, with fibers and other filamentous extracellular components being present in virtually every tissue.
What is important to the present discussion is that softer tissues tear more easily than firmer tissues, so blunt dissection attempts to proceed by exerting sufficient force to tear softer tissue but not firmer tissue.
Blunt dissection can be difficult, tedious, dangerous, and is often time-consuming. Judging the force to tear a soft tissue, but not a closely apposed firm tissue, is not easy. Thus, blood vessels can be torn. Nerves can be stretched or torn. In response, surgeons attempt judicious sharp dissection, but blood vessels, nerves, and airways can be cut, especially the smaller side branches, which become exponentially more common at smaller scales. This all leads to long, tedious dissections and increased risk of complications, like bleeding, air leaks from the lungs, and nerve damage. Complications of blunt dissection are common, as are repairs.
Surgeons frequently use forceps for blunt dissection. Forceps include finger engagers, a pivot, and two jaws for clamping together on tissues, but surgeons often employ forceps in a spreading mode, forcing the jaws apart in an attempt to tear or rend two adjacent tissues apart. This secondary use of forceps is common, but forceps are far from ideal for blunt dissection.
Laparoscopic and thoracoscopic (collectively referred here as “endoscopic”) instruments use a similar action, albeit at the distal end of a very long shaft piercing the patient's body wall through a trocar. This arrangement imposes even more challenges, making laparoscopic blunt dissection more difficult, lengthening the time of procedures, and increasing the chances of intraoperative complications.
For either instrument, forceps 10 or endoscopic forceps 10, a surgeon performs blunt dissection by closing the forceps, pushing the closed forceps into a tissue and then, optionally, opening the forceps inside the tissue, using the force applied by opening of the jaws of the forceps to tear the tissue apart. A surgeon thus proceeds to dissect a tissue by a combination of pushing into the tissue and opening the jaws of the forceps.
Blunt dissection is commonly used for wet and slick tissues, and the smooth, passive surfaces of most surgical instruments slide easily along the tissue, impairing the instrument's ability to gain purchase and separate the tissue. Furthermore, the surgeon has only limited control, being able only to jab, move sideways, or separate. An improved instrument for blunt dissection that could differentially separate soft tissues while not disrupting firm tissues would greatly facilitate many surgeries. Of further utility would be an improved instrument that was as simple as possible, getting the job done with as few moving parts as can be achieved, whilst increasing both safety and speed.